Question1993 Jeep Grand Cherokee - V8 5.2 L automatic
Idles horribly, usually only after it warms up. When I first start it, it idles fast, then after it warms up it will cycle back and forth low to high, almost rhytmically. Will often stall when I put it into gear. Seems to run fine when up to speed (don't notice any misfires). I was told the O2 sensor might be the culprit but was also told that the check engine light usually comes on for that and it is not on. I'm wondering if it's clogged injector(s). Tried some expensive B&F (?) additive but that did nothing. Thanks, Jeff
AnswerIt IS possible that it could be an o2 sensor fault that may not turn ON the check engine light of which is why you have to hand test the sensor(s) using a QUALITY digital volt meter and tie into the o2 sensor circuit to monitor it's operation.
My thoughts lean more towards a residue buildup around the throttle plate area of which is very common and or a residue buildup within the IDLE AIR circuitry air passages.
You can purchase an aerosol cleaner from most any auto parts store and clean the throttle plate area and if you notice right near the throttle plate you will see a PIN HOLE in the inside of the chamber of which is your IDLE AIR BY-PASS HOLE. Spray this cleaner into this hole also.
There is also the possibility that you have a vacuum leak somewhere within the intake manifold and or due to a loose or broken vacuum line in one of the numerous rubber and plastic lines that are on the engine.
What mechanical work or ANY kind of work has been performed on the vehicle recently ?. As most problems that occur after a recent repair was made can be traced back to the area of where the repair was made as a vacuum line may have been knocked loose or a wire connection came loose, Look around in the area where work was performed.
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